Note 4 - Supplementary Cash Flow Information - Supplementary Cash Flow Elements (Details) - USD ($)	9 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Apr. 30, 2018	Apr. 30, 2017
Cash and cash equivalents	$ 4,364,000	$ 4,218,000	$ 5,941,000
Restricted cash	469,000	469,000
Total cash, cash equivalents, and restricted cash shown in the Consolidated Condensed Statement of Cash Flows	4,833,000	4,687,000	$ 6,410,000	$ 7,026,000
State and local income tax payments	230,000	232,000
Federal income tax payments to the Parent	$ 2,050,000	$ 3,450,000